A known example of this kind of measurement device that requires calibration of its biosensor, is a urine measurement device that measures the urinary sugar level of urine that is directly applied to the biosensor during urination (refer to Japanese patent application H9-297120). In other words, since the sensitivity of the biosensor changes according to the amount of time elapsed, frequency of use such as the number of times used or length of time used, or the environment such as temperature or storage conditions, it becomes necessary to calibrate the reference value that becomes a reference during measurement (hereafter, referred to as the ‘measurement reference value’).
Generally, this kind of measurement device determines whether or not calibration of the sensitivity is necessary according to the frequency of use of the biosensor, and when calibration is necessary, notifies and prompts the user to perform calibration. In this calibration of the sensitivity, output from the biosensor for a reference fluid is obtained. That is, when measuring a reference fluid, the user drips some reference fluid from a dropper shaped container onto the biosensor, and the output from the biosensor after doing this is obtained by the measurement device that comprises that biosensor.
After measuring this reference fluid, it is necessary that the biosensor, (1) first, be cleaned in a cleaning fluid, (2) then immersed in a preservative fluid such as a buffer fluid, and (3) allowed time for the baseline of the output to become stable. (Hereafter, the process of these steps (1) to (3) will be referred to as the ‘cleaning process’.)
However, normally, sensitivity calibration is seldom completed after one measurement of the reference fluid. For example, when only a small amount of reference fluid that is applied to the biosensor, that amount might not be enough to satisfy the required amount needed for measurement. In that case, the output value from the biosensor is not used for sensitivity calibration and the measurement device displays a message that measurement of the reference fluid must be performed again.
Despite this, the cleaning process was performed each time the reference fluid was applied. This is so that no reference fluid remains in the biosensor in order that the measurement of the reference fluid performed next will be performed under the same measurement conditions. In this kind of sensitivity calibration, the work of performing the cleaning process must be performed, which takes time.